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authorSasha Levin <levinsasha928@gmail.com>2012-05-29 15:06:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-29 16:22:18 -0700
commit08fa29d916c6e271ad13978cd993e7238c68db97 (patch)
treea7f7aa9a3a468cba985e5a26551b504f48e2922e
parent4c9c6a1bc869daeb1575442cbf94ba5878c08a67 (diff)
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mm: fix NULL ptr deref when walking hugepages
A missing validation of the value returned by find_vma() could cause a NULL ptr dereference when walking the pagetable. This is triggerable from usermode by a simple user by trying to read a page info out of /proc/pid/pagemap which doesn't exist. Introduced by commit 025c5b2451e4 ("thp: optimize away unnecessary page table locking"). Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: David Rientjes <rientjes@google.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: <stable@vger.kernel.org> [3.4.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/task_mmu.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 1030a716d155..7faaf2acc570 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -784,7 +784,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
/* find the first VMA at or above 'addr' */
vma = find_vma(walk->mm, addr);
- if (pmd_trans_huge_lock(pmd, vma) == 1) {
+ if (vma && pmd_trans_huge_lock(pmd, vma) == 1) {
for (; addr != end; addr += PAGE_SIZE) {
unsigned long offset;